package com.yangcangclub.commons.utils;

public class IdWorker {
    private final long workerId;
    private final static long twepoch = 1303895660503L;
    private long sequence = 0L;
    private final static long workerIdBits = 10L;
    private final static long maxWorkerId = -1L ^ -1L << workerIdBits;
    private final static long sequenceBits = 12L;

    private final static long workerIdShift = sequenceBits;
    private final static long timestampLeftShift = sequenceBits + workerIdBits;
    private final static long sequenceMask = -1L ^ -1L << sequenceBits;

    private long lastTimestamp = -1L;


    public IdWorker(final long workerId) {
        super();
        if (workerId > this.maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0",
                    this.maxWorkerId));
        }
        this.workerId = workerId;
    }


    public synchronized long nextId() {
        long timestamp = this.timeGen();
        if (this.lastTimestamp == timestamp) {
            this.sequence = this.sequence + 1 & this.sequenceMask;
            if (this.sequence == 0) {
                timestamp = this.tilNextMillis(this.lastTimestamp);
            }
        }
        else {
            this.sequence = 0;
        }
        if (timestamp < this.lastTimestamp) {
            throw new RuntimeException((String.format(
                    "Clock moved backwards.  Refusing to generate id for %d milliseconds", this.lastTimestamp - timestamp)),null);
        }

        this.lastTimestamp = timestamp;
        return timestamp - twepoch << this.timestampLeftShift | this.workerId << this.workerIdShift | this.sequence;
    }


    private long tilNextMillis(final long lastTimestamp) {
        long timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }


    private long timeGen() {
        return System.nanoTime() / 1000000;
    }

    public static void main(String[] args) {
        String id=""+new IdWorker(3).nextId();
        id=id.substring(id.length()-16);
        System.out.println(id);
    }
}